Abstract: Prolonged sitting without proper repositioning in a wheelchair results in excessive pressure over the ischial tuberosities and coccyx significantly increasing the risk of pressure ulcers (PU), which impose a tremendous burden in terms of cost and the quality of life and the functional activities of the long-term wheelchair-bound population. Unrelieved pressure has been identified as the major etiological factor of developing PU for long-term care residents. We propose to evaluate a new seat design for wheelchair, in which the back part of the seat can be dynamically tilted downward with respect to the front part of the seat to be able to release the sitting interface pressure over the ischium. The mechanism introduces a novel concept in controlled sitting and has been demonstrated the capability to largely release the sitting interface pressure under the ischium and promote tissue viability. Therefore, we plan to evaluate this sitting mechanism in reducing the PU risk and accelerating PU healing rate in wheelchair-bound spinal cord injury (SCI) patients. In the long run, we expect it to help increase the quality of the life and promote functional status for long time wheelchair users. Specific aim 1: To evaluate sitting interface pressure distributions between the buttock-thighs and seat, between the back and backrest, and the load shift on the seat and back, during sitting in the proposed wheelchair and compare with those of usual wheelchair sitting. Specific aim 2: To evaluate tissue viability by way of measuring tissue perfusion and skin temperature changes during sitting with wheelchair equipped with the proposed mechanism and compare with those of usual wheelchair sitting plus clinically recommended Push-up regimen. Research for specific aim 1 and 2 will be carried out on 2 groups of wheelchair users with SCI, chronic and acute. Specific aim 3: To evaluate PU healing rate when using wheelchair equipped with the proposed mechanism and compare with those of usual wheelchair sitting plus push-ups. A group of wheelchair users with SCI who have PU developed in sitting area will be included. PU healing process evaluation will be carried out when using the proposed sitting mechanism and comparing that with a controlled group of similar patients using regular wheelchair. Specific aim 4: To evaluate the preferences in sitting posture when sitting with wheelchair equipped with the proposed mechanism versus sitting in the usual posture plus clinically recommended Push-up regimen. Chronic SCI patients included in the above studies will be asked to complete a questionnaire for subjective evaluation about the comfort and tolerance related sitting in the proposed mechanism and compare it with the usual wheelchair.